A new facile method that employs high-power sonication is used to break, up firmly agglutinated nanodiamonds and obtain dispersion just as effectively as stirred-media milling. ne dispersion properties of the de-agglutinated nanodiamonds in various nonaqueous solvents, and the pH-dependent dispersion/precipitation behavior of the hydrosols are presented (see figure). The brownish color of the colloids is attributed mostly to the Rayleigh scattering superimposed over the finite absorption in the visible wavelength.